Simultaneous-exposure stereophotographic fundus camera



- [72] inventor United States Patent John H. McMillin 116 Hollywood,Monroe, Michigan 48161 211 AppLNo. 632,742

[22] Filed Aplllzl, 1967 [45] Patented Oct. 13,1970

[54] SlMULTANEOUS-EXPOSURE STEREOPHOTOGRAPHIC FUNDUS CAMERA 2 Claims, 14Drawing Figs.

Donaldson A New Camera for Stereoscopic Fundus photography Archives ofOphthalmology vol. 73.22 pp. 253- 267 Primary ExaminerNorton AnsherAssistant Examiner-Richard M. Sheer Attorney- Barthel and BugbeeABSTRACT: A stereophotographic fundus camera is disclosed wherein theexposures for both views of the same eye at separated distances forsubsequent stereoscopic viewing are made simultaneously side-by-sideupon the same film in proper arrangement for viewing without subsequentjuxtaposition. The nose of the camera contains a light masking disc orwall with three apertures therein, two of which are upper, laterallyspaced apertures and the third of which is a lower aperture immediatelybelow and midway between the upper apertures. Illumination of the fundusfor focusing is made by light from a single electric light bulbproceeding by way of a condenser and collimating lens system through thelower hole into the eye with the light passing through the flash bulbwhich is to be subsequently ignited for making the exposure. Thereturning ray bundles after reflection from the fundus and refractionthrough the ocular optical system pass through the two upper laterallyspaced holes in the mask. The thusseparated ray bundles pass throughrhomboidal prisms, thence through separate focusing objective opticalsystems, including a second set of rhomboidal prisms and focusingcomponents of the objective optical system, to laterally spacedstationary mirrors which reflect the rays upward to a swinging frontsurface mirror. The latter in its upper position serves as an occludingshutter closing laterally spaced openings into the film chamberimmediately overhead, and at the same time reflecting the rays to andthrough the laterally spaced eye pieces of the viewing optical systememployed for visual observation and focusing. This swinging mirror, whenswung down into a substantially vertical position, energizes the flashbulb to make the exposure and opens the film chamber to permit theimages of the fundus to be projected onto the laterally spaced areas orframes of the film and, when swung upward, closes the film chamber.Transporting of the film to present a new pair of frames is performedina conventional manner. The camera nose containing the masking discrests, during operation, in a recess in the front of an 'aperturedspeculum curved rearwardly to fit under the eyelids and against thesclera of the eye being photographed, after the eye has beenanaesthetized to tolerate the presence of the speculum, and its pupildilated by a mvdriatic.

Patented Oct. 13, 1970 Sheet 2 INVENTOR JOHN H. McMlLL I N ATTORNEYSPmmed 0a. 13, 1910 3,533,342

Sheet 1 0:4

JOHN H.McMlLLl N ATTORNEYS SIMULTANEOUS-EXPOSURE STEREOPHOTOGRAPIIICFUNDUS CAMERA Prior stereophotographs of the fundus were made with asingle frame camera which was shifted laterally between successiveexposures to make the two laterally separated views necessary forsteroscopic viewing. This necessarily presupposed that the eye wouldremain immovable and its condition unchanged between exposures,assumptions which were not always valid. Prior efforts to simultaneouslyexpose these two stereoscopic views have been obstructed by thedifficulty of getting adequate illumination into the eye and adequatesizes of ray bundles emerging from the eye after reflection from thefundus, even when the pupil of the eye has been dilated. The soleexample of a simultaneous exposure stereoscopic fundus camera known tothis inventor was that described and illustrated in Archives ofOphthalmology, Volume 73, No. 2 in an article by David D. Donaldson,M.D. entitled New Camera for Stereoscopic Fundus Photography on pages253 to 267 thereof.

SUMMARY OF THE INVENTION This instrument is both a binocular (stereo)ophthalmoscope and a stereo fundus camera. As the image of the fundus isautomatically erected by the optical system within the camera, it isseen by the ophthalmologist as it would appear to him when seen througha direct ophalmoscope, with the added value of three-dimensionalviewing. For these reasons, the present camera produces stereoscopiccolor slides which can be viewed immediately after development withoutrequiring image juxtaposition, thereby reducing the time and laborpreviously required in preparing stereoscopic slides. The presentcamera, by providing simultaneously exposed stereoscopic colorphotographs of the fundus, thereby eliminates the delays in moving priorcameras the stereoscopic separation distances between successiveexposures. By this camera, the

FIG. 7 is a fragmentary rear elevation of the upper portionophthalmologist photographically records in 'three-dimensional color thedetails of the fundus with such accuracy that progress pictures taken atintervals provide an internist with periodic records, either of furtherdegeneration or, hopefully, of improvement after treatment, especiallyin cases of systemic disease in which the fundus findings are the mostaccurate guide to prognosis, as in arterial hypertension of in diabetes.The speculum bringsthe nose of the camera the closest to the anteriorcorneal surface without ever touching it. It thus properly positions thecamera, prevents interference from blinking, and with the aid of thetarget, assures that all pictures will be identical except forindividual differences or pathological changes, for fundus markings havebeen held to be as characteristic as fingerprints. Moreover, the use ofthe so-called M-3 flash bulb instead of the more expensive andcomplicated electroniqflash tube simplifies both the construction andoperation of the camera.

In the drawings:

I FIG. 1 is a schematic top plan view of the optical system of asimultaneous exposure stereophotographic fundus camera, according to oneform of the invention;

FIG. 2 is a central vertical section through the stereophotographicfundus camera optical system of FIG. 1, taken along the line 2-2therein;

FIG. 3 is a central vertical section through the stereophotographicfundus camera employing the optical system of FIGS. 1 and 2, taken alongthe line 3-3 in FIG. 5;

FIG. 4 is a top plan view of one half of the stereophotographic funduscamera of. FIG. 3, taken along the line 4-4 in FIG. 3, the other halfbeing identical but of opposite arrangement;

FIG. 5 is a front elevation partly in section of the stereophotographicfundus camera taken along the line 5-5 in FIG. 3, with details of theshutter mechanism, shown fully in FIGS. 12 and 13, omitted to simplifythe disclosure;

FIG. 6 is a detail front elevation of the camera nose masking disc ofFIG. 3, looking in the direction of the arrows 6-6 therein;

direction of the arrows 7-7 in FIG. 3;

FIG. 8 is a fragmentary vertical longitudinal section through thebattery compartment, taken along the line 8-8 in FIG. 5;

FIG. 9 is a fragmentary side elevation of the locking device for thefilm compartment, looking in the direction of the arrows 9-9 in FIG. 5;

FIG. 10 is a fragmentary vertical longitudinal section through the rearwall of the film transport winding compartment, taken along the line10-10 in FIG. 5;

FIG. 11 is a horizontal section through the film compartment, takenalong the line 11-11 in FIG. 5, with certain portions of the filmtransport winding mechanism shown in horizontal section in a slightlylower plane;

FIG. 12 is a vertical longitudinal section showing in side elevation theswinging mirror-shutter mechanism, taken along the line 12-12 in FIGS. 5and 11;

FIG. 13 is a vertical cross section taken along the line 13-13 in FIG.12; and

FIG. 14 is a diagrammatic vertical section identical with the upperleft-hand portion of FIG. 3, showing the nose of the camera restingagainst a speculum which in turn engages the marginal portion of theeyeball beneath the eyelids.

Referring to the drawings in detail, FIGS. 3, 4 and 5 show asimultaneous exposure stereophotographic fundus camera, generallydesignated 20, of the present invention as consisting generally of asupporting structure 22 carrying an illuminating system 24 and also astationary optical unit 26 of a stereophotographicand viewing opticalsystem 28. The latter includes a movable optical unit 30 mounted in andtraveling unitarily with a movable camera housing 32. The stereoscopicphotographic and viewing optical system 28 (FIG. 1) consists of twoidentical subsystems 29 and 31 arranged in two laterally spacedoppositely offset predominantly parallel paths. These subsystems, aswill be evident from the drawings and description below, focus a pair ofindependently erected images in a focal plane through which the filmemulsion surface passes and in properly separated spacing forstereoscopic viewing.

ILLUMINATING SYSTEM The supporting structure 22 includes a stand 34 ofwhich only the upright post 36 is shown. Any suitable conventional standmay be used, preferably the swinging arm of a refracting stand or theconventional tripod stand used in physical and ophthalmologicalinstruments. The upper end of the post 36 is seated in a socket 38 in anelongated horizontal base 40 and clamped therein as by the clampingscrew 42. The socket 38 is formed in a boss on the base 40, the forwardend of which is counterbored at 44 (FIG. 3) to receive a flash bulbsocket 46 forming a part of the illuminating system 28, and drilled asat 48 for the passage of wires (not shown) leading to the socket contactfor engaging the base 50 of a conventional transparent flash bulb orfilm-exposure light emitter 52. Rearwardly and above the flash bulbsocket 46, the base 40 is drilled to receive a stop pin 54 for limitingthe forward travel of the camera housing 32 containing the movableoptical unit 30.

' Bolted or otherwise removably secured to the foreward end of the base40 is an upper lamp house 56 enclosing the flash bulb 52 and removablefor replacement of burned out flash bulbs 52. Mounted in the upper lamphouse 56 is a condensing lens 58 for collecting the light rays from anelectric light bulb or viewing light emitter or illuminator 60. Theelectric light bulb 60 in turn is housed in a lower lamp house 62 joinedat 64 to the upper lamp house 56 and having a lower cup-shaped a sourceof low-voltage electric current (not shown). Such low voltage electriccurrent is conveniently supplied from the low voltage winding of aconventional stepdown transformer, the

high voltage winding of which is connected to a conventional houselighting circuit outlet (not shown). Such low voltage is convenientlysix volts or twelve volts for safety reasons and also is'employed to"fire" the flash bulb 52 at the proper instant by way of wires throughthe passages 48. as explained more fully below.

The upper and lower lamp houses 56 and 62 collectively form anillumination housing 74 which is so mounted on the base 40 as to beslidable horizontally to permit access to the flash bulb 52 in order toreplace it after firing. The upper end of the upper lamp house 56 isprovided with a shouldered opening or window 76 adapted to receive anoptical filter 77 optionally used. and aligned with a corresponding.opening or window 78 leading into the fixed lower part 80 (FIG. 3) of astationary optical housing 82, the upper part 84 o f1 which is removableto gain access to the stationary unit 26 of the stereophotographicoptical system 28. Mounted in the lower part 80 of the stationaryoptical housing 82 above the opening 78 is a front surface mirror 86 soinclined relatively to the axis 88 of the illuminating system 24 as toreflect the ray bundle from the condenser 58 through an illuminatingsystem objective or projection lens 90, such as the two-component lensshown in the upper left-hand corner of FIG. 3. and thence through thelower central aperture 92 in an opaque mask disc 94 into the interior ofthe eye being photographed. The masking disc 94 not only screens thecamera against the entrance of extraneous undesired light reflected fromthe cornea of the eye being photographed but also serves as a locatingelement for the camera in the manner described below.

The masking disc 94 (FIG. 6) is circular and has a circular recess 96.The lower central aperture or illuminating light exit aperture 92 opensinto the recess 96 below the center thereof. whereas above and onopposite sides of that center are two horizontally spaced closelyadjacent returning light entrance apertures 98 through which passes thelight reflected from the fundus and refracted by the optical system ofthe eye. and enters the stereophotographic and viewing optical system28. The masking disc 94 fits into a corresponding recess in an aperturedspeculum curved to fit the sclera of the eye under examination andhaving its margin adapted to extend beneath the eyelids. Such a speculumis shown in FIGS. 6, 7 and 8 of my US. Pat. No. 2,586,973 issued Feb.26. I952 for "Fundus Camera Including Eye Fixation Means."

PHOTOGRAPHIC AND VIEWING OPTICAL SYSTEM The base 40 (FIGS. 3 and isprovided with an elongated central upstanding dovetail guide rib 100over which a movable dovetail slide 102 snugly but slidably fits..Iournaled transversely in the slide 102 is a pinion 104 on a shaft 106terminating in a focusing knob 108 (FIG. 5). The dovetail guide rib 100is centrally grooved for the major portion of its length to receive arack bar 110 (FIG. 3) bolted therein from beneath and having teethmeshing with the pinion 104. The slide 102 is in the form of anelongated block with the downwardly facing dovetail groove 112 thereofextending from end to end (FIGS. 3 and 5). The movable camera housing 32is bolted to the dovetail slide 102 to move unitarily therewith inresponse to the rotation of the focusing knob 108 and contains themovable unit of the optical system 28.

The stationary optical unit 26 (FIGS. 1 to 4 inclusive) is mounted inthe stationary housing 82 and consists of a pair of oppositely-inclinedrhomboidal prisms 114 which receive the two pencils or rays emergingfrom the two entrance apertures 98 and reflect them through objectivelenses 116. which are focused directly upon the fundus, in combinationwith the optical system of the eye. Each objective lens 116 consists ofa plane-convex forward element 118, a concavo-convex intermediateelement 120 and a biconvex rear element 122' separated by air spaces.The movable optical unit 30, on the other hand, likewise is paired andconsists of a pair of imageerecting subsystems 124, each including aplano-convex field lens I26, a rhomboidal prism I28, and an air-spacedtripleelement lens 130. each consisting of a plane-convex forwardclement I32. a biconcave intermediate element 134. and a biconv xrearward element 136. From each triple element lens 130. the ray-pencilsare reflected perpendiculary upward by a pair of front surfacestationary mirrors 138 to the image plane or focal plane I40 (FIG. 2)occupied by the front emulsion surface 141 ofthe photographic film I42(FIGS. 5 and 11 unless barred from doing so by a swinging mirror-shutter144 (FIG. 3) described below.

Each field lens 126 is mounted at the forward end ofa tubu Iar mountingstructure or cell 146 (FIG. 3). the rearward end of which is recessedinto and secured to the forward wall 148 of the movable camera housing32. which is provided with a pair of laterally spaced openings 150 forthe passage of the Extending horizontally across the camera housing 32between its opposite side walls 162 and rearwardly from the front wall148 partway to the rear wall 164 thereof is an inter mediate wall 166.Extending across and secured to the rearward edge of the intermediatewall 166 is an inclined stop strip or bar 168, the rearward face ofwhich is cushioned against the impact of the forward edge of theupwardly swinging mirrorshutter 144. The mechanism which actuates thelatter to swing it around its pivot axis 170 (FIG. 3) is describedbelow. Meanwhile, it is sufficient to state that in its raised or solidline position resting against the cushioned stop strip 168, the frontsurface mirror 172, with its reflecting surface 173 forming thereflecting portion of the mirror-shutter I44 and secured to the pivotedplate 174, shuts off the light from the film chamber 176 (FIG. 3) andinstead reflects the ray bundles rearwardly in a horizontal direction toand through their respective eyepieces or oculars. 178 by which theimagery is viewed by the operator. The focal'plane 140 is located at thesame axial distance from the stationary mirrors 138 as the focal planeof the eyepieces 178.

Each eyepiece 178 consists optically of a biconvex forward element 180,an intermediate air-spaced biconcave element 3 182 and a rearwardair-spaced plano-convex element 184.

These elements collectively constitute each eyepiece lens 186. Eacheyepiece lens 186 is mounted in a tubular eyepiece cell 188, the reduceddiameter forward portion of which is mounted in a tubular support 190which in turn is held in an apertured tubular mount 192. The two mounts192 are similar in shape and construction. but are oppositely arrangedas regards their integral arms 194 (FIG. 7) which are disposed parallelto one another in vertically spaced overlapping relationship. The mounts192 for the purpose of providing a pupil- Iary distance adjustment forthe operator are laterally movable toward and away from one anotherbetween upper and lower guide grooves 196 and 198 (FIGS. 3 and 7) in anapertured guide plate 200 secured to the rear wall 164 of the camerahousing 32 and held in these guide grooves 196 and 198 by retainingstrips 202 and 204 respectively. Threaded into the guide plate 200 inthe approximate midportion thereof between the arms 194 is a pivot screw206 which pivotally supports a bent hand lever 208. The upright portionof the bent hand lever is drilled with over sized holes at equallyspaced distances from the pivot screw 206 for the loose passage ofscrews 210, the excessive clearance providing, in

effect, a pin-and-slot connection to compensate for the varying radiiinvolved in the swinging of the hand lever 208. The

ported thereby in opposite directions for interpupillary distanceadjustment.

Mounted in the focal plane of each lens 186 of each eyepiece 178 is anilluminated ophthalmic fixation target plate 214 of transparent materialand provided at its intersection with the optical axis of each eyepiecelens 186 with a fixation target 216. The latter may consist of anindentation or scratch, or etched or molded cross. depending on whetherthe fixation plate 214 is constructed of glass or transparent plastic.Leading upward tothe lower edge of each target plate 214 is a passageway218 (FIGS. 3 and 7) in the rear wall 164 of the camera housing 32, eachpassageway 218 being counterbored at its lower end to receive aminiature electric light bulb 220 of the type having an integral lens inthe tip thereof. such as is used in otoscopes. Each light bulb 220 isengaged by a spring contact finger 222 secured at 224 to the recessbottom wall 154.

Each of the anchor screws 224 of the spring contact fingers 222 isconnected through wiring (not shown) to a fixed contact 226 (FIG. 8) ina battery compartment 228 located at one end of the camera housing 32(FIG. 5) and closed by an access plate 230. The other fixed contact 232is connected by wiring (not shown) to the sides of the counterbores 234in which the light bulbs 220 are located and which their sides engage inelectrically conducting relationship. The contact portions of thecounterbores 234 are of course insulated from the circuit containing thespring fingers 222. Mounted in the battery compartment 228, which is anextension of the camera housing 32, are two juxtaposed dry cells 236(FIG. 8). their ends opposite the ends engaging the fixed contacts 226and 232 being electrically interconnected by an approximately V- shapedspring member 238 bolted to a wall of the battery compartment 228.

MIRROR-SHUTTER CONSTRUCTION The mechnanism 240 (FIGS. 3. 5, I2 and 13)operates the mirror-shutter 144 which includes the front surface mirror172 and a supporting plate 174 pivoted to swing downward on thehorizontal axis 170 in the dotted line position arcuate path (FIG. 3).In its upper solid line position it reflects the imageforming raysthrough the eyepieces 178 and at the same time obstructs the passage oflight to the film chamber 176 in order to avoid fogging the film 142therein. When, however, the mirror-shutter 144 is momentarily swungdownward into its vertical position, it trips the actuator lever 237 ofa microswitch 239 mounted on the bottom wall 154 between the fixedmirrors 138, igniting the flash bulb 52. The actual duration of exposureis governed by the "duration peak" of the flash bulb, which is 17.5milliseconds with the M-3 bulbs.

Rotatably mounted as at 242 and 243 in the opposite side walls 162(FIGS. 3, 5 and 12) is a pivot shaft 241, one side of which is cut awayto provide a flat chordal surface 244 upon which the plate 174 ismounted in a plane parallel to the pivot axis 170 of the pivot shaft241. The surface 244 is so spaced away from the pivot axis 170 as tocause the plane of the front surface 173 of the movable front surfacemirror l72 to pass through the pivot axis 170. Mounted on the outer end242 of the pivot shaft 241 is a crank arm 246 (FIG. 12) having an angledand rounded contact tip 248. A relatively weak spring 250, as explainedbelow, but sufficient strong to overcome the weight of themirror-shutter 144, urges the pivot shaft 241 in a counterclockwisedirection and the crank arm 246 toward its upper position shown in solidlines in FIG. 12.

The left-hand side wall 162 is bored as at 252 to receive a steppedbearing sleeve 254 containing a longitudinal bearing bore 256, the axis258 of which is disposed in spaced parallel relationship with the pivotaxis 170 of the mirror-shutter pivot shaft 241. Rotatably mounted in thebore 256 is a shutter operating shaft 260 on the inner end of which ismounted a collar 262 keyed, pinned or otherwise drivingly securedthereto. Surrounding the reduced diameter innermost portion of thebearing sleeve 254 is a strong torsion spring 264 (FIG. 13), one end ofwhich is anchored to the adjacent side wall 162 and the other end to thecollar 262 so as to urge the shutter-operating shaft 260 to rotate in acounterclockwise direction (FIG. 12). The spring 264 is termed strong'in the sense that it is sufficient to overpower the so-called "weak"spring 250 and swing the crank arm 246 and mirror-shutter 144 downwardas shown by the dotted line position thereof in FIG. 12.

In order to so engage and swing the crank arm 246 downward. there ismounted on and keyed or pinned or otherwise drivingly secured to theshutter-operating shaft 260 the hub 265 of a carrier disc 266. Near itsperiphery, the carrier disc 266 is drilled parallel to the axis 258 ofthe shaft 260 to receive a stepped pivot stud bolt 268. Pivotallymounted on the enlarged shank portion of the pivot bolt 268 is anacuteangled bellcrank lever 270. The bellcrank lever 270 has a lower arm272 with an arcuately-cutout inner edge 274 adapted to provide clearancefor swinging of the bellcrank lever 270 around its pivot bolt 268 and atthe same time clear the hub 265 of the disc 266. The inner arcuate edge274 is also the inner edge of the upper arm 276 of the bellcrank lever270 which also has a concavely-arcuate outer edge 278 to provideclearance for the upward swinging of the crank arm tip 248. The upperarm 276 has an approximately radial contact end 280 adapted to engageand slide past the rounded contact tip 248 of the crank arm 246 and anarcuate cam edge 282 disposed approximately at right angles theretosufficient to clear the rounded tip 248 when the contact end 280 haspushed the crank lever 246 downward to its dotted line position, asexplained below in connection with the operation of the invention.

Mounted on the carrier disc 266 and engaging the lower or outer end ofthe lower arm 272 of the bellcrank lever 270 is a spring 284 whichnormally urges the arcuate inner edge 274 of the lower arm 272 againstthe hub 265 of the carrier disc 266, but permits yielding in theopposite direction in order to permit the arcuate cam portion 282 of theupper arm 276 to yield while sliding past the rounded tip 248 of thecrank arm 246 during operation. Secured as by welding 'to the carrierdisc 266 in a' chordal position relatively thereto is a shuttercockingarm 286 (FIGS. 12 and 13) which, when pressed downward from its dottedline to its solid line position of FIG. 12 winds up the torsion spring264 (FIG. 13) by rotating the shutter-operating shaft 260 and cocks theshutter. The shutter carrier disc 266 is drilled parallel to its axisnear its periphery and held in its cocked position by a locking lug orpin 288 (FIG. 13) which serves as a catch for engaging a notch 290 inthe upper edge of a shutter release lever 292 which is drilled near itsforward end to receive a pivot stud screw 294 threaded into acorrespondingly-drilled and threaded hole 296 in the adjacent side wall162 (FIG. 13). The lower edge of the shutter release lever 292 isengaged and urged upward around the pivot screw 294 in a clockwisedirection by the upper arm.

of a torsion spring 298 pressing against a lug 300 on said lower edge,the spring 298 encircling the screw 294 and having its lower armanchored in a hole 302 near the bottomedge of the adjacent side wall162. Depressing the shutter release lever 292 pulls the notch 290 awayfrom thepin 288 and releases the carrier disc 266 to operate the shutterand make an exposure in the manner described below in connection withthe operation of the invention.

FILM WINDING AND REWINDING MECHANISM The film winding and rewindingmechanism, generally designated 304, shown in FIGS. 3 to 5 and 9 to 11inclusive is housed in the top of the camera housing 32 above a top wallits emulsion 141 facing downward is pressed downward by a pressure plate314 so as to lie in the image plane or focal plane 140. The pressureplate 314 is resiliently urged downward upon the film 142 by leafsprings 316 attached to the underside of the cover 318 of the camerahousing 32. Projecting longitudinally from each end of the cover 318near the corners thereof are two laterally spaced lugs 317 and 319.

Secured to each of the opposite ends of the camera housing cover 318 isa slidable releasable locking channel plate 321 (FIGS. 5,9 and 11).Threaded into each of the outer'end walls of the film housings 320 and322 are two horizontally-spaced stud screws 323 whose smooth shankportions pass through aligned elongated slots 325 (FIG. 9) in eachlocking plate 321, which has a bent handle end 327. Formed in the upperflange of each channel plate 321 near the end 329 opposite the handleend 327 is a rectangular notch 331 slightly longer than the width of theadjacent lug 317. Shifting each locking plate 321 in FIG. 9 until thenotch 331 registers with the adjacent lug 317 while the handle end 327completely uncovers the opposite end lug 319, enables the opposite endsof the camera housing cover 318 to be lifted from their interfittingrib-andgroove connections with the top plate 306. The cover plate 318may then be lifted off to remove an exposed film cartridge and replaceit with an unexposed cartridge, as explained more fully below. Thecamera housing 32 adjacent the opposite ends ofthe top wall 306 isprovided with a pair of open-topped box-shaped unexposed and exposedfilm housings 320 and 322 respectively secured to and depending from thetop wall 306.

The film housing 320 contains an unexposed film chamber 324 for anunexposed film cartridge 326 (FIG. 11), the film from which proceedsupward, with the emulsion 141 down, through the image plane or focalplane'140 across the top surface 310 of the top wall 306 and downwardinto an exposed film chamber 328 into which the film 142 is wound aftereach exposure. The top wall 306 is provided with a guide groove 330through which the film 142 travels between the shouldered side walls ofthe guide groove 330. Rotatably mounted in the exposed film chamber 328is an exposed film winding drum or spool 332 (FIG. 11) drivinglyconnected by a set screw 334 to a shaft 336 journaled in a bore 338 inthe front wall 148 of the camera housing 32 and having a winding knob340 bolted or otherwise drivingly secured thereto. The drum or spool 332is provided with a film-end-engaging toothed spring clip 333. Theopposite end of the shaft 336 is journaled in the recessed rearward wall164 of the camera housing 32 and bolted or otherwise drivingly securedthereto is a toothed gear wheel 342 engaged by the pointed tip 344 (FIG.of a locking pawl 346. The pawl 346 is pivoted intermediate its oppositeends upon a pivot screw 348 threaded into the rear wall 164 and itslower end 350 projects downward outside and below the exposed filmhousing 322. One arm of a U-spring 352 engages and urges the upper endand pointed tip 344 of the pawl 346 into locking engagement with theteeth of the gear wheel 342 while the opposite arm thereof is bolted orotherwise secured to the side wall 354 of the recess 356 in the rearwall 164 of the camera housing 32. The recess 356 is closed by a coverplate 358.

The exposure counting mechanism, generally designated 360 (FIGS. 5, 10and 11) includes a window 362 in the cover plate 358 through which isseen one of six exposure numbers on the periphery of a rotaryexposure-indicating disc 364 for a -exposure cartridge 326. Theexposure-counting disc 364 is loosely and rotatably mounted upon a pivotstud screw 366 (FIGS. 10 and 11) and is drivingly secured to a gearwheel 368 which meshes with the gear wheel 342. A convexo-concave orbowed spring washer 370 is mounted on the stud screw 366 adjacent thewall 164 and engages the gear wheel 368 for exerting frictional pressureupon the gear wheel 368 and exposure-indicating disc 364.

.lo'urnaled in the rear wall 366 of the unexposed film housing 320 (FIG.11) is an axle 369 having a notched inner end 371 engageable with theusual diametral rib 372 on the outer end of the film spool (not shown)within the film cartridge 326. Drivingly secured to the axle 369, as bythe setscrew 374, is a film rewinding knob 376. The axle 369 may bepulled outward to disengage its notched end 371 from the spool rib 372and also to remove it entirely from the film cartridge 326 in order toinsert another cartridge in reloading, whereupon the knob 376 and axle369 may be pushed inward (FIG. 11) to reengage the notched end 371 withthe spool rib 372.

As the effective relative aperture of the photographic optical system ofthis camera is approximately f/l7, the correspondingly great depth offocus may render accurate focusing difficult for some operators.Accordingly, a scale (not shown) calibrated in diopters(+. .0. .)ismounted on the opposite side of the base 40 from that shown in FIG. 3,with which registers a pointer (also not shown) extending downward fromthe dovetail slide 102. After the refractive error of the eye to bephotographed has been determined, the setting of the camera for focusmay thereby be made with extreme accuracy.

OPERATION In the operation of the invention, let it be assumed that theoperator has inserted an unexposed color film cartridge 326 in thechamber 324 and has threaded the leader strip of the film 142, emulsiondown, through the guide groove 330 in the top wall 306 and has hooked itonto the clip 333 on the exposed film winding drum 332. The operatorthen rotates the winding knob 340 and the winding drum 332 to windthereon the length of fogged leader strip which was exposed outside thefilm cartridge 326 when the film 142 was being threaded. This length offogged film 142 is equivalent to the number of exposures seen in thewindow 362 necessary to equal the length of film initially exposed inthreading it. He then pushes the thumb of his hand against the exposedlower rim portion of the exposure counting disc 364 to rotate it untilthe exposure number I appears in the window opening 362.

The operator now cocks or sets the shutter mechanism 240 by pushingdownward upon the shutter-cocking arm 286, moving it from its upperdotted line position of FIG. 12 to its lower solid line positiontherein. This action rotates the carrier disc 266 through an angle ofapproximately 90 and causes its locking pin 288 to snap into the lockingnotch 290, pushing the shutter release lever 292 downward around itspivot 294 against the urge of the spring 298 until it does so. At thesame time, the rotation of the carrier disc 266 and the consequentrotation of the shaft 260 and collar 262 winds up the stronger torsionspring 264 and brings the bellcrank lever 270 to its solid line positionof FIG. 12. Meanwhile, the spring 284 is pressing the lower arm 272 ofthe bellcrank lever 270 against the disc hub 265 and the weaker spring250 is urging the crank arm 246 and the mirror-shutter 144 into theiruppermost or solid line positions shown in FIGS. 3 and 12.

Meanwhile, the patients eye E (FIG. 14), the fundus F of which is to bephotographed, has been anaesthetized and its pupil P dilated by the useof a mydriatic. The operator then inserts the above-mentioned speculum Sagainst the sclera outside the patients cornea C beneath the eyelids Land brings the nose of the camera 20 adjacent the speculum so that theperiphery of the mask disc 94 interfits with the recess in the front ofthe speculum. The operator then turns on the viewing light bulb 60 androtates the focusing knob 108 to move the movable camera housing 32 andits movable optical unit 30 back and forth while he asks the patient tofix his gaze upon the fixation target 216, which meanwhile has beenilluminated by the energization of the light bulb 220 from the dry cells236.

While this is occurring, the light from the illuminating bulb 60 passesthrough the condenser 58 and flash bulb 52 to the mirror 86 where it isreflected as a parallel-ray pencil through the illuminating systemobjective lens 90 and the lower central hole 92 in the mask disc 94(FIGS. 3 and 6), whence it reaches the cornea, enters the dilated pupilof the patients eye and arrives at the fundus. The light reflected fromthe fundus passes outward through the optical system of the eyeincluding the cornea C and lens thereof and thence emerges and dividesinto two laterally spaced pencils formed by the two laterally spacedholes 98 in the mask disc 94. These ray pencils are displaced laterallyby the rhomboidal prisms 114 (FIG. 1) and are caused to becomeconvergent by the objective lenses 116 in the stationary optical unit26. These convergent ray pencils. proceeding along parallel opticalaxcs.,are brought to a focus in the viewing focal plane coincident withthe fixation target 216 after refraction and image erection, by thepositive field without requiring this to be done manually by subsequentoperations, as in conventional stereoscopes.

When the operator, while looking through the eyepieces 186 and rotatingthe focusing knob 108, obtains a clear and sharp image of the fundus asthe patients gaze is fixed upon the fixation target 216, the operatordepresses the shutter release lever 292 (FIG. 12), causing the lockingnotch 290 therein to move downward away from the pin or lug 288,unlocking the carrier disc 266, Under the torque of the torsion spring264, the disc 266 rotates rapidly in a counterclockwise direction.causing the front end 280 of the upper arm 276 of the bellcrank lever270 to engage the rounded tip 248 and push downward upon it, itsstronger spring 264 overpowering the weaker spring 250 and swinging thecrank arm 246 and mirror-shutter 144 from their solid line positions totheir dotted line positions (FIGS. 3 and 12) through an angle of about45 degrees. When the mirror-shutter 144 swings downward into itsapproximately vertical position, it pushes downward upon the microswitchactuating lever 237, closing the microswitch 239 and firing the flashbulb 52. Meanwhile, the ray bundles pass upward into the film chamber176 and through the circular framing apertures 308 onto the filmemulsion 141 in the focal plane 140, exposing the film 142.

When the lowermost position of the crank arm 246 is reached, the roundedtip 248, which meanwhile has been sliding approximately radially acrossthe bellcrank lever end 280, reaches the corner thereof and slides off,whereupon the weaker spring 250 swings the mirror shutter I44 upwardagainst the stop bar 168, terminating the exposure. The operator or hisassistant then rotates the winding knob 340 until a new exposure numberon the exposure counting disc 364 appears in the window 362. A newexposure may then be made, and so on until the film 142 in the filmcartridge 326 is completely exposed. To photograph the fundus of thepatients other eye, the foregoing procedure is repeated with the othereye anaesthetized, its pupil dilated and the speculum inserted therein.

When the film cartridge 326 has been completely exposed, as indicated bythe final number appearing in the window 362, the operator pushes thehandle 350 of the locking pawl 346 to the left to withdraw the pointedtip 344 thereof out of locking engagement with the gear wheel 342 whileat the same time he rotates the rewinding knob 376 to consequentlyrotate the spool (not shown) inside the film cartridge 326 and thusrewind the film l42 back into the cartridge 326 in a manner similar tothat carried out with conventional 35 mm. photographic cameras, He thenremoves the exposed cartridge 326 by pulling the knob 376 and axle 369out of the cartridge 326 (FIG. 11), after which he unlocks and lifts offthe cover 318, in the manner described above, and inserts an unexposedcartridge 326 in its place.

From the foregoing description and drawings it may be observed that thefirst pair ofimages formed by the objective lenses 116 of the stationaryoptical unit 26 are focused upon the forward faces of their respectivefield lenses 126 which are movable for focusing. These images areerected by the imageerecting subsystems ll-land fall on the film imageplane or focal plane 140.

l claim:

1. A simultaneous-exposure stereophotographic fundus camera for takinginstantaneous stereoscopic photographs of the fundus of the eye, saidcamera comprising a speculum having a marginal portion which is curvedrearwardly around a central opening to fit against the sclera and behindthe eyelids of the eye being photographed and also having on the frontthereof a camera-locating portion,

a camera housinghaving a rearward housing structure con' taining a filmcompartment with film holding and transporting means therein and aforward housing structure extending forwardly from said rearwardstructure and terminating forwardly in a nose portion of reduced sizeconfigured to be inserted beneath the eyebrow and engage and fit thecamera-locating portion of the speculum engaging the eye beingphotographed, said nose portion containing a light exit aperture and apair oflight entranceapertures,

said apertures being spaced apart from one another but disposed closelyadjacent to one another and of sufficiently small size to pass anincident light ray pencil through the exit aperture and speculum openingand receive a pair of refracted light ray pencils passing out throughthe dilated pupil of an eye disposed adjacent thereto forstereophotography and through the speculum opening and entranceapertures;

an illuminating optical system aligned with said exit aperture andincluding a light source arranged to project an illuminating light raypencil through said exit aperture;

a stereophotographic optical system containing two independent opticalsubsystems mounted in spaced predominantly parallel axis relationship insaid housing and including oppositely-facing reflectors arranged towiden the separation of said refracted pencils a plurality of timestheir initial separation while passing through said en trance apertures,

said optical subsystems including objective lenses adapted to be focuseddirectly upon the fundus of the eye in combination with the opticalsystem of the eye,

said optical subsystems being constructed and arranged to focus a pairof stereoscopic images of the fundus on a photographic focal plane onthe film in positions at separations adapted for stereoscopic yviewing:I j V a pair of laterally spaced eyepieces disposed coaxial with saidoptical subsystems at focal distances therefrom corresponding to thefocal distance therefrom of said photographic image plane; and

a movable reflector movable from a position shielding said photographicimage plane and film from the light rays emergent from said opticalsubsystems and directing said rays into said eyepieces to a positionexposing said photographic image plane to said emergent rays.

2. A simultaneous-exposure stereophotographic fundus camera, accordingto claim 1, wherein a shutter is disposed between said photographicfocal plane and said optical subsystems, and wherein said illuminatingoptical system light source includes a translucent viewing light emitterand an independent translucent film-exposure light emitter disposed intandem along the optical axis of-said illuminating optical system withthe light from one emitted adapted to pass through the other emitter onits way to said exit aperture, and means for operating saidfilm-exposure light emitter in timed relationship with said shutter.

